Various types of detersive enzymes have long been conventionally used in laundry detergents to assist in the removal of certain stains from fabrics. These stains are typically associated with lipid and protein soils. The enzymes, however, have proven less effective against other types of soils and stains.
It has also long been known that peroxygen bleaches are effective for stain and/or soil removal from fabrics, but that such bleaches are temperature dependent. At a laundry liquor temperature of 60.degree. C., peroxygen bleaches are only partially effective. As the laundry liquor temperature is lowered below 60.degree. C., peroxygen bleaches become relatively ineffective. As a consequence, there has been a substantial amount of industrial research to develop bleaching systems which contain an activator that renders peroxygen bleaches effective at laundry liquor temperatures below 60.degree. C.
Numerous substances have been disclosed in the art as effective bleach activators. One widely-used activator is tetraacetyl ethylene diamine (TAED). TAED provides effective hydrophilic cleaning especially on beverage stains, but has limited performance on dingy, yellow stains such as those resulting from body oils. Fortunately, another type of activator, such as nonanoyloxybenzenesulfonate (NOBS) and other activators which generally comprise long chain alkyl moieties, is hydrophobic in nature and provides excellent performance on dingy stains.
It would seem that a combination of enzymes with either hydrophilic or hydrophobic bleach activators, or both, would provide an effective "all-around" detergent composition which would perform well on most types of soils and stains. However, a hindrance to the development of such all-around cleaning compositions has been the discovery that many of the hydrophobic bleach activators developed thus far can promote damage to natural rubber parts used in certain washing machines. Because of the negative effects on washing machine parts, the selection of such detergent-added bleaching systems has been limited. This is especially true for European detergent/bleaches, since many washing machines manufactured in Europe are equipped with key parts, such as sump hoses and motor gaskets, made of natural rubber.
Another problem in developing an all-around cleaning composition has been finding a cleaning agent that is effective under heavy soil load conditions. The removal of heavy soil levels, especially nucleophilic and body soils, has proven especially difficult for conventional bleaching systems. Under such circumstances, conventional activators such as NOBS appear to interact with, and be destroyed by, heavy soil loads before they can optimally provide their intended bleaching function. Still another problem has been the stability of enzymes, especially lipases and proteases, in the presence of bleaches.
A need, therefore, exists for compositions which provide effective cleaning performance over a wide variety of soils and stains. Moreover, the compositions should provide effective cleaning performance without substantially damaging natural rubber machine parts. In addition, the compositions should provide both bleaching performance and enzyme cleaning performance.
Without intending to be limited by theory, it is believed that typical hydrophobic bleach activators undergo a perhydrolysis reaction to form a peroxyacid bleaching agent. However, a typical by-product of the perhydrolysis reaction between conventional bleach activators and hydrogen peroxide is a diacylperoxide (DAP) species. Unfortunately, DAP species derived from hydrophobic activators tend to be insoluble, poorly dispersible, oily materials which form a residue which can deposit on the natural rubber machine parts that are exposed to the laundry liquor. The oily DAP residue can form a film on the natural rubber machine parts and promote free radical and peroxide damage to the rubber, which eventually leads to failure of the parts.
By the present invention, it has now been discovered that the class of hydrophobic bleach activators derived from amido acids forms hydrophobic amido peracids upon perhydrolysis without the production of harmful, oily DAP's. Again, while not intending to be limited by theory, it is believed that the DAP's produced by the perhydrolysis reaction of the amido acid-derived bleach activators used herein are insoluble crystalline solids. The solids do not form a coating film; therefore, the natural rubber parts are not exposed to the DAP's for extended periods of time and remain substantially undamaged.
In addition to the amido acid-derived bleach activators, it has also now been discovered that the class of bleach activators derived from N-acyl caprolactams provide both hydrophilic and hydrophobic bleaching action without the production of harmful DAP by-products.
Additionally, it has also now been discovered that the class of benzoxazin-type leach activators provide effective hydrophobic bleaching action without the production of harmful DAP by-products.
Surprisingly, it has also been discovered that certain enzymes, particularly lipase enzymes, are compatible with these classes of bleach activators.
Accordingly, the present invention solves the long-standing need for detergent compositions which provide efficient and effective performance over a wide range of cleaning needs. The invention also provides efficient and effective detergent compositions for use in washing machines which have parts made of natural rubber, such that the natural rubber is substantially undamaged by the bleaching system. These and other benefits are secured by the invention, as will be seen hereinafter.